Hydraulic mining system

ABSTRACT

This specification discloses an hydraulic mining system including a method and apparatus whereby energy derived from a downflowing column of water utilized to conduct underground mining operations is mechanically transferred to a pump which drives a column of slurry containing mined ore upwardly to a separator on the ground surface.

O United States Patent 1191 1111 3,790,214 Kilroy 1451 Feb. 5, 1974 [54] HYDRAULIC MINING SYSTEM 3,260,548 7/1966 Reichl 299/18 1 B. 5 com 1211221 1:25: 1:21 Tucson, Ariz. 85716 [22] Filed: Sept. 29, 1972 Primary Examiner-Ernest R. Pulrser Attorney, Agent, or Firm-John A. Robertson; Eric P. [21] Appl. NO.2 293,401 schellin 52 us. c1 299/8, 60/398, 61/19, ABSTRACT 299/17, 299/18, 299/ 19, 302/14 This specification discloses an hydraulic mining sys- [51] Int. Cl. E21c 41/00, E21c 45/00 tern including a method and apparatus whereby en- [58] Field of Search... 299/8, l7, 18, 56, 57, 64-68, ergy derived from a downflowing column of water uti- 299/19; 60/398; 61/19; 302/14, 15, 16 lized to conduct underground mining operations is mechanically transferred to a pump which drives a [56] References Cited column of slurry containing mined ore upwardly to a UNITED STATES PATENTS separator on the ground surface. 3,617,094 11/ 1971 Kester 302/14 18 Claims, 3 Drawing Figures PATENTED FEB 5 I974 SHEEI 3 0F 3 1 HYDRAULIC MINING SYSTEM BACKGROUND OF THE INVENTION At the present time, with the costs of underground mining increased yearly, the use of hydraulic mining is being reconsidered. It may be the only practical method for mining under certain conditions.

The use of underground tunnels and other types of excavations, such as modified mine workings, for storage reservoirs of water, especially for hydroelectric pump storage projects, is well known.

Also, it is a known technique to break up rock formations by jets of water, the pressure of which can be derived from the head provided by a downflowing tube which communicates at its upper end with a storage pond or lake at or immediately below the ground surface.

The practicality of'conveying mined ore in slurry form is now recognized as is the feasibility of raising an ore-containing slurry from an underground mining site to a separator at or immediately below the ground surface.

The use of pressure autoclaves, where the metal values are leached from the ore which are then substantially stripped from the leach solution, is well known in mining.

It is also important to note that in many localities, the rates for electric power are lower at night than during the normal daytime working hours.

The present invention is founded on the basic concept of mechanically transferring energy derived from a downflowing column of water to a'pump for driving ,an upflowing column' of ore-containing slurry. It is based on the theoretical calculations that a given volume of water flowing downwards into a mine area, then being enslurried with ore, and then returning to the surface, will require a net power input, supplementing the mechanically transferred energy, at a cost which represents substantial operating savings over conventional haulage equipment used in underground mines.

OBJECTS OF THE INVENTION With the foregoing conditions in mind, the present invention has in view the following objectives:

1. To provide, in a method of hydraulic mining, the step of mechanically driving a pump for an upflowing column of ore-containing slurry by energy mechanically derived from a downflowing column of water used in hydraulic mining operations.

2. To provide, in a method of the type noted, the steps of operating a turbine from a downflowing column of water and mechanically driving a pump which moves an ore-containing slurry upwardly from said turbine. Also, to provide, in a preferred method, the supply of auxillary net power input to the system.

3. To provide, in a method of the character described, the step of operating high pressure, rock breaking jets from the downflowing column of water.

. 4. To provide, in a method of the kind described, the step of conveying mined ore and water used in the mining thereof to a slurry mixing tank.

5. To provide, in a method of the type noted, the step of conveying Water from the mining operation to an un derground reservoir into which excess water from the downflowing column also empties.

6. To provide, in a method of the character aforesaid, the step of conveying water from the underground reservoir to the reservoir at the ground surface.

7. To provide, in a method of the kind described, the steps of separating fine particles from the water which is conveyed from the mining operation to the underground reservoir and delivering such separated particles to the slurry mixing tank.

8. To provide, in a method the type noted, the steps of separating the metal values from the slurry by a pres sure autoclave located at or directly beneath the ground surface, separating the spent ore material from the leach solution, stripping the metal values from the leach solution, and returning water from this separating system to the reservoir at the ground surface.

9. To provide, in a method of the type noted, the steps of mining the ore by mechanical mining apparatus, crushing the mined ore and conveying the mined ore to a slurry mixing tank.

10. To provide a method of the kind described in which the slurry mixing tank and pump which delivers water thereto from the underground reservoir is operated by an hydraulic motor which in turn is actuated by the downflowing column of water.

1 1. To provide apparatus for carrying out the above method.

Various other more detailed objects and advantages of the invention, such as arise in connection with carrying out the above ideas in a practical embodiment, will, in part, become apparent, and, in part, be hereafter stated as the description of the invention proceeds.

SUMMARY OF THE INVENTION The foregoing objects are achieved by providing a water reservoir in the form of a lake or pond which is located at or immediately beneath the ground surface. Extending downwardly from this reservoir and preferably in a direction which is substantially vertical is a downflow tube, the lower end of which empties into an underground reservoir located at the lower level of the mining operation. Included in this tube at a location fairly close to the underground reservoir, speaking with reference to the overall length of the tube, is a turbine which is driven by the downflowing column of water in the tube. This turbine is mechanically connected to a pump which drives a column of slurry in an upfiow tube. As an auxillary to the mechanically driven pump is a system for boosting the power requirements to drive the slurry upwards. This is necessary where underground reservoir capacity is not largeenough to hold the additional volume of water necessary to provide the net input power requirement by mechanical transfer. This auxillary system may be driven by electricity, gas, fuel oil, or other forms of energy. The lower end of this tube communicates with a slurry mix tank and the upper end with an ore separating system that includes a pressure autoclave. Water from the latter is conveyed to the reservoir at the ground surface, preferably under gravity action. Rock breaking jets are provided on a mobile carrier and are operated by the pressure of water in a flexible tube that is connected to the downflow tube immediately beneath the turbine therein. Mined ore and water are conveyed by another flexible tube to the slurry mix tank under the influence of a pump which is driven by a motor operating on one of the above auxillary energy forms. Excess water from the mining operation is conveyed by gravity action through a tube to the underground reservoir. A settling tank is included in this tube for the purpose of separating fine particles from the water and these fine particles are delivered to the slurry mix tank. Water for the slurry mix tank is drawn from the underground reservoir by a pump which is driven by a motor operating on one of the above auxillary energy forms. Excess water from the underground reservoir is returned to the surface reservoir by an upflow tube under the influence of a pump that is driven by a motor operating on one of the above energy forms, but electricity is preferred.

In a somewhat modified and perhaps more simplified form of the invention, the ore is mined by conventional mining apparatus, crushed and conveyed to the slurry mix tank. The mining apparatus, rock crusher and conveyor are driven by motors operating on one or more of the above auxillary energy forms.

In another embodiment of the invention, all of the underground operations including the breaking of rocks by water jets, conveyance thereof to the slurry mix tank and the operation of the slurry mix tanks are driven from an hydraulic motor which is in turn actuated by the head of water in the downflow tube. In the latter case, both of the reservoirs should be extensive to allow for the return of water from the underground reservoir to the surface reservoir at night when electric power is less expensive, if available. In addition, the volume of water needed to provide the net power input, provided by other energy forms in the preferred embodiment, will be substantially greater than that used in said preferred embodiment.

For a full and more complete understanding of the invention, reference may be had to the following description and the accompanying drawings wherein:

FIG. 1 is a vertical section through a ground formation with parts broken away and largely diagrammatic of mining apparatus used to carry out the method of this invention;

FIG. 2 is a view similar to FIG. 1 of a modified embodiment, and

FIG. 3 is another view similar to FIGS. 1 and 2 of still another modified embodiment.

Before referring to FIG. 1, it is important to note that each of the three embodiments illustrated disclose a downflow tube and an upflow slurry tube. These elements are illustrated as having a wide angle of divergence. However, it is to be clearly understood that this angle will vary with different terrain and in some instances it may be found to be practical to include them in a single conduit, bore or passage extending from the ground surface to the underground reservoir.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, wherein like reference characters denote corresponding elements throughout the several views, and first more particularly to FIG. 1, a mine site is indicated generally at 10 and includes a ground formation 11 having a top surface 12 and formed with a slightly inclined stope 13 at the lower portion thereof in which the actual mining operation takes place. The mine entrance for personnel is not shown.

Formed at ground surface 12 or immediately therebeneath is a lake or pond forming a surface reservoir 14. This reservoir should be extensive and much larger in relative size than indicated by the diagrammatic representation thereof. It should have a capacity sufficient to provide water for the operations now to be described, with said volume of water being limited to that amount necessary to enslurry a given volume of ore, to fill the operating system, and to provide a minimum surplus as a safety factor. Extending downwardly from surface reservoir 14 is a downflow tube 15 which as illustrated is substantially vertical, although it well could be inclined from the vertical. The lower end of tube 15 opens onto an underground reservoir 16 which also would have a large capacity comparable to that of surface reservoir 14. Included in downflow tube 15, a short distance above underground reservoir 16, is a turbine represented diagrammatically at 17. This turbine is driven by the downflowing water in tube 15.

An upflow slurry tube is designated 18. The lower end of tube 18 communicates with a slurry mix tank 19 and its upper end with an ore separator 20 which includes a pressure autoclave.

Ore, or essentially waste material, which is separated from the slurry passes out one end of the separator 20 as indicated by arrow 21, leach solutions are stripped of metal values and processing chemicals, and the resulting barren water is conveyed from separator 20 by tube 22 which has preferably a slight downward angle of inclination to surface reservoir 14. Thus, the water conducted through tube 22 to surface reservoir 14 is spent, in that it has performed the function required of it.

Included in slurry tube 18 immediately above slurry mix tank 19 is a pump 23. Pump 23 is mechanically driven from turbine 17 by driving connections represented at 24. It is believed unnecessary to herein illustrate or describe details of the mechanical connections 24, because such are generally well known. The auxillary net power input system will be integrated with the mechanical pump 23, with said details also being omitted since such systems are well known. Such auxillary power input may take the form of electric motor 6 which is mechanically connected to pump 23.

Water is delivered to slurry mix tank 19 by a pipe 25 which includes a pump 26 that is driven by an electric motor 27 and the lower end of which communicates with underground reservoir 16.

The ore formation which is being mined is represented at 28 and is illustrated as being at one end of a slightly inclined stope 13. In most instances this ore will contain a large quantity of rock which in the embodiment now being described will be broken up by water emanating from jet nozzles, one of which, representing the general class of high pressure nozzles, is shown at 29. Jet nozzles 29 are mounted on a mobile carrier 30 and water under pressure is supplied by flexible and segmented tube 31 which is connected to downflow tube 15 as indicated at 32. This connection 32 is located between turbine 17 and underground reservoir 16. Another flexible and segmented tube 33 has one end mounted on the carrier 30 immediately adjacent to jet nozzles 29 and its other end to slurry mix tank 19 as indicated at 34. A pump 35 is included in tube 33 and is driven by an electric motor 36. It will be understood that while pump 35 and motor 36 are illustrated diagrammatically, they would be mounted on carrier 30.

Although the most sophisticated and advanced jet cannons disintegrate the rock into fragments small enough to be carried into a slurry acceptable for transport to the surface, an alternative set of machinery would replace scoop at front of carrier 30 if it were necessary to reduce particle size of fragments even further. This machinery would include a rotating set of scoops to drop material onto two counter-moving conveyors that would move material to center of carrier 30. The material would then be moved onto a third conveyor which is 90 to the other two. The material would be moved to the rear of the carrier to be crushed in a wet ball mill 9, mobile like the carrier, or to be moved to a stationary wet ball mill and thence moved to mixing tank 19. The alternative equipment would be driven by electric motors.

A drain tube 37 has an upper end at 38 which opens onto the floor of stope 13 where it receives water re sulting from the jets provided by nozzles 29. Drain tube 37 has a slight downward angle of inclination whereby water may flow therethrough to underground reservoir 16. Included in drain tube 37 is a settling tank 39 in which fine particles which may be suspended in water flowing through drain tube 37 are collected. A transfer tube 40 has one end connected to settling tank 39 as indicated at 41, and its other end to slurry mix tank 19 as indicated at 42. Included in transfer tube 40 is a pump 43 which is driven by an electric motor 44.

A return tube 45 has a lower end communicating with underground reservoir 16 as indicated at 46 and an upper end which communicates with surface reservoir as indicated at 47. Included in return tube l5 is a pump 48 which is driven by an electric motor 49. Thus,

OPERATION OF THE PREFERRED EMBODIMENT While the manner in which the above described apparatus operates to carry out the method of this invention is believed to be obvious from the illustration of FIG. 1 and the description of parts as set forth above, it is briefly outlined as follows:

Surface reservoir 14 contains an adequate amount of water to provide the head and flow for the operations now to be described. water flows downwardly through downflow tube and drives turbine 17. It also supplies water under pressure to tube 31 which in turn supplies the water to jet nozzles 29. Tube 31 pressure is developed by free flow passage of water, downflowing from turbine 17, into connection 32 in a manner that allows water to enter tube 31 without developing enough back pressure to reduce to any significant degree the energy transfer at turbine 17, but whatever energy loss results is made up in the net power input requirements. An alternative for operating purposes and for emergencies is the provision for a second pump at 7, with a bypass line 8 from reservoir 16 to tube 31, said pump preferably being driven by an electric motor which may be the motor 6 as illustrated. The high pressure water jets break up the formation 28, whereupon the broken pieces of ore and some water are sucked into the open end of tube 33 at mobile unit 30 by pump 35, or said material and water are removed and transported as described above, and this mixture of broken ore and Water is conveyed to slurry mix tank 19 by tube 33. In mix tank 19, the ore is further comminuted and additional water supplied through pipe 25 from underground reservoir 16. Thus, ore-containing slurry is drawn into the lower end of slurry tube 18 by pump 23 which is mechanically driven from turbine 17 by connections 2d, and by the auxillary net power input system. The slurry under pressure is delivered to separator 20 in which waste material and metal values are separated from the water. The tailings pass out of the separator as indicated at 211 and the stripped water is returned through tube 22 to surface reservoir 14.

Excess water from the mining operation is collected in a sump, covered by grillwork similar to a cattleguard, provided by end 38 of drain tube 37 and flows through the latter to underground reservoir 16. Fine particles are collected in the settling tank 39 and transferred by tube dll to slurry mix tank 19 by pump 43.

Water from underground reservoir 16 is returned to surface reservoir 17 through tube 45 under the influence of pump 48.

Pumps 26, 4%, auxillary power input at pump 23 and bypass line 31 and pump 7 could be used to fight underground fires, if such an emergency arose.

FIRST MODIFICATION In this embodiment of the invention, the basic elements of the form shown in FIG. 1 are included, with the basic difference residing in the fact that the ore for mation represented at 50 at the end of stope 13 is adapted to be mined by conventional mining apparatus represented graphically at 51. Minted ore is drawn into a crusher 52 and from the latter is dropped onto a conveyor 53 which delivers it to slurry mix tank 19. It will be understood that mining apparatus 51, crusher 52 and conveyor 53 are preferably electrically driven, although the electrical elements are not designated. In this embodiment, the tubes 31, 33 and 40 and their associated devices of FIG. 1 are omitted because they are unnecessary.

The operation of the embodiment of FIG. 2 is sub stantially the same as that described above in connection with FIG. 1 with the notable exception that mining apparatus 51 mines the ore from formation 30, it is crushed in crusher 52 and transferred by conveyor 53 to slurry mix tank 19. Slurry is mixed in the latter and conveyed upwardly in slurry tube 18 by pump 23 in the manner above described in connection with FIG. 1.

SECOND MODIFICATION FIG. 3 discloses a modification which combines some of the features of FIGS. 1 and 2, but which embraces the notable difference that the slurry mix tank is hydraulically actuated.

In the method and apparatus of FIG. 3, the ore formation 2% is broken into pieces by water emanating from jets 29 which is supplied under pressure by flexible tube 31 which has an alternative bypass line 31 with pump at reservoir 16. Jets 29 are mounted on a mobile unit 54 which includes transfer mechanism 55 which delivers the mined ore to a conveyor 56. The latter delivers the ore to slurry mix tank 19'.

Pump 26 is driven by an hydraulic motor 57 which is connected by a nipple 58 with downflow tube I5 immediately below turbine 17.

The operation of the apparatus of FIG. 3 comes quite close to being completely hydraulically operated. The ore is mined hydraulically, the slurry mix tank is operated hydraulically and the slurry is raised by pump 23 which is driven by hydraulically energized turbine 17. Thus, the only preferably electrically operated devices are the transfer mechanism 55, conveyor 56 and pump 43 for settling tank 39.

If the reservoirs l4 and 16 are of sufficient capacities to allow net power input to be developed hydraulically, it will be entirely practical and extremely desirable to conduct the mining operations during the daytime when electric power is costly, but return the water from underground reservoir 16 to surface reservoir 14 at night, when electric power is much less expensive. Thus, great savings in the mining operation may be achieved.

While preferred specific embodiments are herein disclosed, it is to be clearly understood that the invention is not to be limited to the exact steps, mechanisms and devices illustrated and described because various modifications of these details may be provided in putting the invention into practice.

What is claimed is:

1. ln hydraulic mining, the method including the steps of:

a. storing water in a surface reservoir;

b. downflowing a column of water to an underground reservoir;

0. mining ore at an underground level;

d. converting mined ore into slurry at said underground level by combining it with water from said underground reservoir;

e. pumping said slurry upwardly by a pump that is mechanically driven by a turbine that is actuated by said downflowing column of water, with the assistance of an auxillary net power input system, and

f. returning spent water to said surface reservoir.

2. The method of claim 1 in which the ore is mined hydraulically by water jets pressurized by water pumped through a bypass line by a pump.

3. The method of claim 1 in which the slurry is delivered under pressure to an ore separator, including a pressure autoclave, at the ground surface and water from the separator is conveyed to the surface reservoir.

4. The method of claim 1 in which the ore is mined hydraulically by water jets pressurized by water from said downflowing column.

5. The method of claim 4 in which the pressurized water is conveyed from the downflowing column to jet nozzles by a flexible tube and water and mined ore are conveyed to a slurry mix tank by a second flexible tube.

6. The method of claim 5 together with the step of conveying excess water from the locality of the water jets to the underground reservoir.

7. The method of claim 6 together with the steps of separating fine particles from the water that is conveyed from the locality of the water jets to the underground reservoir and transferring said particles to the slurry mix tank.

8. In hydraulic mining, apparatus installed in a ground formation having an upper surface and a lower mining level,

a. a surface reservoir immediately below said upper surface; b. an underground reservoir below said mining level;

c. a downflow tube extending between said reservoirs;

d. a turbine included in said tube at a level closely adjacent to said underground reservoir;

e. a slurry mix tank at said lower level;

f. an upflow slurry tube having a lower end communicating with said slurry mix tank and an upper end at said ground surface;

g. a pump included in said slurry tube;

h. mechanical driving connections between said turbine and pump;

i. net power input apparatus including a motor connected to said pump;

j. ore mining devices at said lower level;

k. means for conveying ore from ore mining devices to said slurry mix tank;

1. a pipe communicating between said underground reservoir and said slurry mix tank, and j 111. means for conveying spent water to said surface reservoir.

9. The mining apparatus of claim 8 together with a separator, including a pressure autoclave, at said upperv ground surface communicating with said slurry tube and a tube between said separator and said surface reservoir.

10. The mining apparatus of claim 8 in which said mining devices comprise jet nozzles, together with a flexible tube extending from saidjet nozzles to said downflow tube and communicating therewith between said turbine and said underground reservoir and in which the means for conveying mined ore to said slurry mix tank comprises a flexible tube including a pump.

11. The mining apparatus of claim 10 together with a drain pipe communicating between the locale of said water jets and said underground reservoir.

12. The mining apparatus of claim 11 together with a settling tank included in said drain pipe, together with a transfer tube communicating between said settling tank and said slurry mix tank and including a pump.

13. The mining apparatus of claim 8 in which the means for conveying spent water to said surface reservoir includes a return tube extending from said underground reservoir to said surface reservoir and including an electrically driven pump.

14. The mining apparatus of claim 8 in which the mining devices are mechanical and the means for conveying ore from the mining devices to the slurry mix tank is a mechanical conveyor.

15. The mining apparatus of claim 8 in which the mining devices are jet nozzles connected to said downflow tube by a flexible tube, the mined ore is conveyed to the slurry mix tank by a mechanical conveyor and water is delivered from said underground reservoir to said slurry mix tank by a pump that is actuated by an hydraulic motor connected to said downflow tube between said turbine and underground reservoir.

16. The mining apparatus of claim 15 together with a return tube communicating between said underground reservoir and said surface reservoir and including an electrically operated pump.

17. The mining apparatus of claim 8 in which said mining devices comprise jet nozzles, together with a flexible tube extending from said jet nozzles to said underground reservoir and being driven by a pump located thereat.

18. The method of claim 1 in which the step of returning spent water to the surface reservoir includes the pumping of water from said underground reservoir to said surface reservoir. 

1. In hydraulic mining, the method including the steps of: a. storing water in a surface reservoir; b. downflowing a column of water to an underground reservoir; c. mining ore at an underground level; d. converting mined ore into slurry at said underground level by combining it with water from said underground reservoir; e. pumping said slurry upwardly by a pump that is mechanically driven by a turbine that is actuated by said downflowing column of water, with the assistance of an auxillary net power input system, and f. returning spent water to said surface reservoir.
 2. The method of claim 1 in which the ore is mined hydraulically by water jets pressurized by water pumped through a bypass line by a pump.
 3. The method of claim 1 in which the slurry is delivered under pressure to an ore separator, including a pressure autoclave, at the ground surface and water from the separator is conveyed to the surface reservoir.
 4. The method of claim 1 in which the ore is mined hydraulically by water jets pressurized by water from said downflowing column.
 5. The method of claim 4 in which the pressurized water is conveyed from the downflowing column to jet nozzles by a flexible tube and water and mined ore are conveyed to a slurry mix tank by a second flexible tube.
 6. The method of claim 5 together with the step of conveying excess water from the locality of the water jets to the underground reservoir.
 7. The method of claim 6 together with the steps of separating fine particles from the water that is conveyed from the locality of the water jets to the underground reservoir and transferring said particles to the slurry mix tank.
 8. In hydraulic mining, apparatus installed in a ground formation having an upper surface and a lower mining level, a. a surface reservoir immediately below said upper surface; b. an underground reservoir below said mining level; c. a downflow tube extending between said reservoirs; d. a turbine included in said tube at a level closely adjacent to said underground reServoir; e. a slurry mix tank at said lower level; f. an upflow slurry tube having a lower end communicating with said slurry mix tank and an upper end at said ground surface; g. a pump included in said slurry tube; h. mechanical driving connections between said turbine and pump; i. net power input apparatus including a motor connected to said pump; j. ore mining devices at said lower level; k. means for conveying ore from ore mining devices to said slurry mix tank; l. a pipe communicating between said underground reservoir and said slurry mix tank, and m. means for conveying spent water to said surface reservoir.
 9. The mining apparatus of claim 8 together with a separator, including a pressure autoclave, at said upper ground surface communicating with said slurry tube and a tube between said separator and said surface reservoir.
 10. The mining apparatus of claim 8 in which said mining devices comprise jet nozzles, together with a flexible tube extending from said jet nozzles to said downflow tube and communicating therewith between said turbine and said underground reservoir and in which the means for conveying mined ore to said slurry mix tank comprises a flexible tube including a pump.
 11. The mining apparatus of claim 10 together with a drain pipe communicating between the locale of said water jets and said underground reservoir.
 12. The mining apparatus of claim 11 together with a settling tank included in said drain pipe, together with a transfer tube communicating between said settling tank and said slurry mix tank and including a pump.
 13. The mining apparatus of claim 8 in which the means for conveying spent water to said surface reservoir includes a return tube extending from said underground reservoir to said surface reservoir and including an electrically driven pump.
 14. The mining apparatus of claim 8 in which the mining devices are mechanical and the means for conveying ore from the mining devices to the slurry mix tank is a mechanical conveyor.
 15. The mining apparatus of claim 8 in which the mining devices are jet nozzles connected to said downflow tube by a flexible tube, the mined ore is conveyed to the slurry mix tank by a mechanical conveyor and water is delivered from said underground reservoir to said slurry mix tank by a pump that is actuated by an hydraulic motor connected to said downflow tube between said turbine and underground reservoir.
 16. The mining apparatus of claim 15 together with a return tube communicating between said underground reservoir and said surface reservoir and including an electrically operated pump.
 17. The mining apparatus of claim 8 in which said mining devices comprise jet nozzles, together with a flexible tube extending from said jet nozzles to said underground reservoir and being driven by a pump located thereat.
 18. The method of claim 1 in which the step of returning spent water to the surface reservoir includes the pumping of water from said underground reservoir to said surface reservoir. 